The winger, who was named Belgian Jupiler Pro League Player of the Year last season following a prolific campaign, was left out of Brugge's squad for their pre-season friendly against Heerenveen as the move edges towards completion.
Tzolis is set to join the Premier League champions in a deal worth around £34m, becoming Arsenal's first attacking signing of the summer as they look to replace Leandro Trossard, who completed a move to Turkish side Besiktas earlier this week. The 24-year-old enjoyed a spectacular campaign for Brugge last season, recording 22 goals and 29 assists in 52 appearances across all competitions as the club won their 20th Belgian Pro League title.
Leko spoke warmly about Tzolis's development and the significance of the move for both player and club.
"It's a fantastic example, someone who was first coming to the training base, whose last training session was like a game for him, giving so much for his career. Then you get to go to sign for one of the biggest clubs in Europe, big thing for him, big thing for Club Brugge and big thing for Belgian football," he said.
The Brugge coach also framed the transfer as an example for the club's younger players to follow.
"Good lesson for all young boys that in football you need to work, stop to talk, work, try to do everything to improve yourself day by day," Leko said, before reflecting on the bittersweet nature of losing one of his key performers.
"On one side I'm very happy for him but very sad for me as we are losing a top player. I am convinced that he will have his minutes that he will show on highest level in Premier League and Champions League that he will show he's a top player and that he absolutely deserves to be there."
Tzolis previously spent time in English football with Norwich City before returning to continental Europe, and his displays for both Brugge and Greece's national team, for whom he has scored nine goals in 34 caps, made him a target for several clubs before Arsenal moved to secure his signature.
He is set to replace Trossard directly in Mikel Arteta's squad and will provide competition for a starting berth in Arsenal's forward line as the club continues to reshape its attacking options ahead of the new season.